This invention generally relates to furnaces and more particularly to cooling systems therefore.
Air-cooling or water cooling of the walls or shell of an industrial furnace is an almost universally accepted technique and is used in furnaces of all types, e.g., stationary, rotary, etc., capacities and for all types of fuel and methods of firing. Thus, one common practice is to cool the walls or shell of an industrial furnace via the use a plurality of external fans focused thereon. This technique has its drawbacks, e.g., complexity, inefficiency, non-uniformity of air flow, fan noise, etc. Another type of air cooling involves the induction of air about the furnace shell. In particular with this technique a sheet metal hood is provided about the furnace and an exhaust fan coupled to the hood to pull cooling air into the area between the hood and the furnace shell. In order to maximize the cooling effects large amounts of air are required, thereby necessitating a large fan. Moreover, this technique still leaves much to be desired from the standpoints of efficiency and uniformity of the air flow within the hood/shell.
Water-cooling of furnaces walls has been used and is generally more effective than air cooling techniques. The water cooling of the furnace wall reduces the mean temperature of the structural members and, consequently, their temperatures are kept within the limits that provide satisfactory strength and resistance to oxidation, while reducing heat transfer to the furnace surroundings. Water-cooled tube constructions facilitate large furnace dimensions and optimum arrangements of the furnace roof, hopper, and arch, as well as the mountings for the burners and the provision for screens, platens, or division walls to increase the amount of heat-absorbing surface exposed in the combustion zone. External heat losses are small and are further reduced by the use of insulation.
Prior art methods utilizing water-cooled furnace walls include constructions utilizing water-containing tube constructions surrounding the exterior of the furnace shell and are commonly referred to as the tangent tube, welded membrane and tube, flat stud and tube, full stud and refractory-covered tube and the tube and tile-type construction. T. Baumeister, Marks' Standard Handbook for Mechanical Engineers, 7th Ed., McGraw-Hill (1967).
Other prior art methods of cooling an industrial-type furnace with water include the use of multiple spigots or spray lances which spray water on the exterior of the furnace shell from above. The water vaporizes as it hits the furnace shell and any water which does not vaporize upon contact runs down the sides of the shell where it may vaporize. The water's evaporation reduces the shell temperature. This method of shell cooling, while generally better than air cooling, is never the less somewhat inefficient and suffers from numerous drawbacks and hazards, e.g., non-uniformity of cooling, producing an uncontrolled amount of steam into the environment, causing water to run onto the floor, etc.
Accordingly, a need exists for an efficient furnace shell cooling system to be used in cooling an industrial type furnace.